SECURITIES AND EXCHANGE COMMISSION Washington, DC 20549 SCHEDULE 13G Under the Securities Exchange Act of 1934 (Amendment No. 6) Principal Financial Group (Name of Issuer) Common Stock, $0.01 Par (Title of Class of Securities) 74251V 10 2 (CUSIP Number) Check the following box if a fee is being paid with this statement [ ]. CUSIP No. 74251V 10 2 13G Page 2 of 6 Pages 1 Name of Reporting Person S.S. or I.R.S. Identification No. of above person Northern Trust Corporation 36-2723087 The Northern Trust Company 36-1561860 Northern Trust, NA 36-3190871 Northern Trust Bank, FSB 38-3424562 Northern Trust Investments, N.A. 36-3608252 Northern Trust Company of Connecticut 06-6275604 Northern Trust Global Investments Ltd 6807764922343A00 2 Check the appropriate box if a member of a group Not Applicable (a) (b) 3 S.E.C. use only 4 Citizenship or place of organization Northern Trust Corporation--a Delaware corporation with principal offices in Chicago, Illinois Number of Shares Beneficially owned by Each Reporting Person With 5 Sole Voting Power 12,682,564 6 Shared Voting Power 1,501,275 7 Sole Dispositive Power 13,547,112 8 Shared Dispositive Power 545,796 9 Aggregate amount beneficially owned by each reporting person 14,297,574 10 Check box if the aggregate amount in Row (9) excludes certain shares. Not Applicable 11 Percent of class represented by amount in Row 9 5.46 12 Type of reporting person Northern Trust Corporation HC SECURITIES AND EXCHANGE COMMISSION Washington, DC 20549 SCHEDULE 13G UNDER THE SECURITIES EXCHANGE ACT OF 1934 Check the following box if a fee is being paid with statement [ ]. 1. (a) Principal Financial Group (Name of Issuer) (b) 711 High Street, Des Moines, IA 50392 (Address of Issuer's Principal Executive Office) 2. (a) Northern Trust Corporation (Name of Person Filing) (b) 50 South LaSalle Street, Chicago, Illinois 60603 (Address of Person Filing) (c) U.S. (Delaware Corporation) (Citizenship) (d) Common Stock, $0.01 Par (Title of Class of Securities) (e) 74251V 10 2 (CUSIP Number) 3. This statement is being filed by Northern Trust Corporation as a Parent Holding Company in accordance with S240.13d-1(b) (1) (ii) (G). 4. (a) 14,297,574 (Amount Beneficially Owned) (b) 5.46 (Percent of Class) (c) Number of shares as to which such person has: (i) 12,682,564 (Sole Power to Vote or to Direct the Vote) (ii) 1,501,275 (Shared Power to Vote or to Direct the Vote) (iii) 13,547,112 (Sole Power to Dispose or Direct Disposition) (iv) 545,796 (Shared Power to Dispose or Direct Disposition) 5. If this statement is being filed to report the fact that as of the date hereof the reporting person has ceased to be the beneficial owner of more than 5 percent of the class of securities, check the following: [ ] 6. Statement regarding ownership of 5 percent or more on behalf of another person: 7. Parent Holding Company reporting on behalf of the following subsidiaries, all of which are banks as defined in Section 3(a) (6) of the Act: The Northern Trust Company 50 South LaSalle Street Chicago, IL 60603 Northern Trust N.A. 700 Brickell Avenue Miami, FL 33131 Northern Trust Bank, FSB 10 West Long Lake Road Bloomfield Hills, Michigan 48304 Northern Trust Investments, N.A. 50 South LaSalle Street Chicago, IL 60603 Northern Trust Company of Connecticut 300 Atlantic Street, Suite 400 Stamford, CT 06901 Northern Trust Global Investments Ltd 6 Devonshire Square, London, UK EC2M 4YE 8. Identification and Classification of Members of the Group. Not Applicable. 9. Notice of Dissolution of Group. Not Applicable. 10. By signing below I certify that, to the best of my knowledge and belief, the securities referred to above were acquired in the ordinary course of business and were not acquired for the purpose of and do not have the effect of changing or influencing the control of the issuer of such securities and were not acquired in connection with or as a participant in any transaction having such purpose or effect. After reasonable inquiry and to the best of my knowledge and belief, I certify that the information set forth in this statement is true, complete and correct. NORTHERN TRUST CORPORATION ________________________________ By: Orie L. Dudley DATED: 02-08-2008 Title:Executive Vice President and Chief Investment Officer EXHIBIT TO SCHEDULE 13G AMENDMENT FILED BY NORTHERN TRUST CORPORATION Securities and Exchange Commission 450 Fifth Street, N.W. Washington, DC 20549-1004 Attention: Filing Desk, Stop 1-4 RE: Principal Financial Group Pursuant to the requirement of 240.13d-1(k) (1) (iii), this exhibit shall constitute our written agreement that the Schedule 13G to which this exhibit is attached is filed on behalf of Northern Trust Corporation and of its subsidiary(ies), as stated below, regarding our respective beneficial ownership in the above-captioned equity security. NORTHERN TRUST CORPORATION _________________________________ By: Orie L. Dudley DATED: 02-08-2008 Title:Executive Vice President and Chief Investment Officer The NORTHERN TRUST COMPANY NORTHERN TRUST INVESTMENTS, N.A. NORTHERN TRUST GLOBAL INVESTMENTS LTD ________________________________________ By: Orie L. Dudley Title: Executive Vice President and Chief Investment Officer NORTHERN TRUST NA ________________________________________ By: Jacobo Schatz As its Authorized Representative NORTHERN TRUST BANK, FSB ________________________________________ By: Brian J. Hofmann As its Authorized Representative NORTHERN TRUST COMPANY OF CONNECTICUT ________________________________________ By: Trista D Simoncek As its Vice President